Messenger RNA is being isolated for use in an in vitro, cell free system, for the production of procollagen alpha-chains. The intact alpha-chains will be used to examine questions related to the initial assembly of three such chains into complete, helical collagen molecules. A second approach will continue the study of ribosomally bound nascent chains in an effort to determine the intracellular lows of triple helix formation. The role of procollagen or partially degraded procollagen in extracellular fibril formation will be studied in both in vitro and in vivo systems.